CN102494123A - Method for determining transmission ratio of economical gear of stepped speed changer - Google Patents

Abstract

The invention discloses a method for determining the transmission ratio of an economical gear of a stepped transmission, which belongs to the technical field of vehicle control. The present invention is based on the basic theory of automobile running. To make the engine have good fuel economy, it is necessary to keep the transmission ratio of the speed changer and the running speed of the automobile:

The transmission ratio is controlled through the combined feedback of load and road condition changes, so that the engine runs along the economical line to the greatest extent. The automatic mechanical transmission is determined according to the engine torque and speed signals collected by the vehicle speed sensor and combined with the collected vehicle speed signal v _a Output the power P _e of the engine, operate the clutch to connect the transmission, perform shift control, and determine the economical shift point. The invention makes the engine have good fuel economy. The method can be used in the design and control of gear shifting in automatic mechanical transmissions.

Description

The Method of Determining the Transmission Ratio of Economical Gear in Stepped Transmission

technical field

The invention belongs to vehicle control technology, in particular to a method for determining the transmission ratio of an economic gear of a stepped transmission.

Background technique

Improving the matching of vehicles and engines is one of the key aspects of energy saving. In normal use, the engine is often in a low-load working state, especially for vehicles on urban road conditions, which makes the fuel economy poor. At present, many large automobile companies in the world are working hard to improve the technical and economic performance of automobiles, reduce the fuel consumption of automobiles, and improve the economical efficiency of vehicles.

When the vehicle is actually running, the throttle opening of the engine is larger only when accelerating, and in most cases the vehicle is only moving at a constant speed. At this time, the power of the engine is not large, so the throttle opening of the engine is small. It can be seen from the universal characteristics of the engine that when the throttle opening is small, the fuel consumption rate of the engine is relatively high, which not only reduces the fuel economy of the vehicle, but also increases the exhaust gas emitted by the engine. Therefore, the ideal control scheme is not to increase the engine speed when the vehicle speed is increased, but to increase the load rate only by changing the gear, so that the engine can work in the low fuel consumption area as much as possible. On a certain road, the fuel consumption is different when the car runs in different gears, so it is very important to choose the appropriate gear. The invention provides a method for determining the transmission ratio of an economical gear of a stepped transmission.

Contents of the invention

The purpose of the present invention is to provide a method for determining the transmission ratio of the economical gear of a stepped transmission, which is characterized in that, in actual use, according to the actual load of the vehicle, the gear is replaced in a timely manner by using the universal characteristic curve of the engine, so that The engine works along the ideal economical operation line; for the continuously variable transmission, the automatic change of the transmission ratio makes the engine run according to the ideal operating curve, and it is always in the most economical load and speed zone to ensure the economy of the vehicle; while for the stepped transmission , it is necessary to control the transmission ratio through the combined feedback of load and road conditions, so that the engine can run along the economical line to the greatest extent. To make the engine have good fuel economy, the ratio between the transmission ratio of the stepped transmission and the driving speed There is the following relationship between:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; rn</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula

i _g —gear ratio of transmission; r—radius of wheel;

v _a ——the relative speed of the vehicle movement, that is, the vehicle's driving speed v, m/s when there is no wind;

n——rotational speed at the minimum fuel consumption point of the engine; i ₀ ——transmission ratio of final drive.

The vehicle economical operation line is composed of the connection points of each equal power hyperbola and the tangent line of the isofuel consumption line, and the vehicle economical operation line is described by a piecewise linear function:

T _e =A _i n+B _i (2)

In the formula

A _i , B _i —constants determined according to the data of the engine type;

T _e ——engine output torque, N·m; n——engine speed, r/min.

According to formula (1):

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 9549</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; rn</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Based on the joint solutions of the above three equations (2), (3) and (4), the approximate ideal economical operation transmission ratio can be obtained as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; (</span>\sqrt{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 38196</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; Pe</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Compare the obtained transmission ratio with the transmission of the sample car, and take the higher gear close to this value as the current gear;

x＝min|i _g -i _x | (6)

Among them, P _i is the engine power when the engine output torque;

The constants A _i and B _i determined according to the data of the engine type are for any engine, according to the above formulas (1)-(6), the best economical characteristic diagram is obtained through experiments, and after it is approximated, it can be Obtain A _i and _Bi in the formula (2); then determine the power P _e of the engine according to the engine torque and speed signals collected by the sensor, and combine the vehicle speed signal v _a collected by the load and road condition changes, according to the formula (5 ) to calculate the required transmission ratio, and then determine the current gear according to the formula (6), so that the engine runs along the economical operation line to the greatest extent.

The beneficial effect of the invention is that the transmission ratio of the transmission can be controlled through the combined feedback of load and road condition changes in the vehicle with the stepped transmission, so that the engine can run along the economical running line to the greatest extent, and the engine can have good fuel economy. The method can be used in the design and control of the shifting of the automatic mechanical transmission (Automated Mechanical transmission, AMT), and is used to determine the economical shift point.

Description of drawings

Figure 1 is a diagram of the best economic characteristics.

Figure 2 is a simplified diagram of optimal fuel economy.

Figure 3 is a schematic diagram of the control.

Detailed ways

The invention provides a method for determining the transmission ratio of the economical gear of a stepped transmission, which is characterized in that, based on the basic theory of automobile driving, in order to make the engine have good fuel economy, it is necessary to make the transmission ratio of the transmission and the driving speed of the automobile. There are the following relations:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; rn</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula

i _g —gear ratio of transmission; r—radius of wheel;

v _a ——the relative speed of the vehicle movement, that is, the vehicle's driving speed v, m/s when there is no wind;

n——rotational speed at the minimum fuel consumption point of the engine; i ₀ ——transmission ratio of final drive.

In actual use, according to the actual load of the vehicle, using the universal characteristic curve of the engine, changing the gear in time can make the engine work along a more ideal economical line. For the continuously variable transmission, the automatic change of the transmission ratio can make the engine run according to the ideal operating curve (as shown in Figure 1), and it is always in the most economical load and speed zone to ensure the economy of the vehicle; while for the existing stepped The transmission needs to control the transmission ratio through the combined feedback of load and road condition changes, so that the engine can run along the economical line to the greatest extent, and the universal characteristic curve and its simplified diagram of the best fuel economy characteristics (as shown in Figure 2 ), the economic running line of the vehicle in the figure is composed of the connection points of each hyperbola of equal power and the tangent line of the equal fuel consumption line; the simplified line can be described by a piecewise linear function:

T _e =A _i n+B _i (2)

In the formula

A _i , B _i —constants determined according to the data of the engine type;

T _e ——engine output torque, N·m; n——engine speed, r/min.

according to:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; 9549</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

According to formula (1):

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; rn</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Based on the joint solution of the above three equations (2), (3) and (4), the approximate ideal economical operation transmission ratio can be obtained as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.377</span>}\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; (</span>\sqrt{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 38196</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; Pe</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Compare the obtained transmission ratio with the transmission of the sample car, and take the higher gear close to this value as the current gear.

x＝min|i _g -i _x | (6)

As shown in Fig. 3, the automatic mechanical transmission (Automated Mechanical transmission, AMT) determines the power P _e of the engine according to the engine torque and speed signals collected by the vehicle speed sensor and combined with the collected vehicle speed signal v _a . For any engine, The best economical characteristic diagram shown in Figure 1 can be obtained through experiments, and after approximation, A _i and _Bi in formula (2) can be obtained, and then the required transmission ratio can be calculated according to formula 5, and then according to Formula 6 determines the current gear, operates the clutch to connect the transmission, executes shift control, and determines the economical shift point (as shown in Figure 2).

Of course, from the universal characteristic curve Figure 1 and the above formula (1), it can be seen that when the engine load rate is low, the fuel consumption rate g _e value increases significantly, and the continuously variable transmission can make the engine in the most economical load and speed zone (etc. The innermost circle of g _e line) to ensure the economy of the engine. Therefore, in order to ensure fuel economy, the most ideal is to use stepless transmission.

Claims (2)

1. definite method of a step change transmission economy retaining velocity ratio is characterized in that in actual use, the actual load according to vehicle utilizes universal characteristic curve of engine, in time changes gear, and motor is done along comparatively ideal economical operation lineman; Automatic change through velocity ratio makes motor according to desirable operation curve operation for stepless speed variator, is in most economical load and rotating speed district all the time, the Economy of assurance vehicle; And for step change transmission; Just need feed back and control transmission ratio through the combination of load and road condition change; Motor is moved along the economical operation line to the full extent; Make motor have good fuel economy, following relation arranged between the velocity ratio of step change transmission and the automobile driving speed:

$i_g=0.377\frac{\mathrm{rn}}{i_0{v}_a}---\left(1\right)$

In the formula

i _g---transmission ratio; R---radius of wheel;

v _a---the relative velocity of vehicle movement, the travelling speed v of automobile when calm, m/s;

N---motor consumption minimization point rotating speed; i ₀---the velocity ratio of main reducing gear.

Said vehicle economical operation line is to be made up of each constant power hyperbola and the tie point that waits oil consumption line tangent line, and this vehicle economical operation line is described with the segmented line shape function:

T _e＝A _in+B _i (2)

In the formula

A _i, B _i---the constant definite according to the data of engine type;

T _e---engine output torque, Nm; N---engine speed, r/min.

Have according to (1) formula:

$P_e=\frac{T_{e}n}{9549}---\left(3\right)$

$v_a=0.377\frac{\mathrm{rn}}{i_0{i}_g}---\left(4\right)$

Separate with above-mentioned (2), three equations couplet of (3) and (4) formula, the economical operation velocity ratio that can get approximate ideal is:

With equation (2) substitution (3), can get:

$P_e=\frac{T_{e}n}{9549}=\frac{(A_{i}n+B)n}{9549}$

Can get according to equation (4):

Therefore: $P_e=\frac{T_{e}n}{9549}=\frac{(A_{i}n+B)n}{9549}=\frac{1}{9549}(A_i\frac{v_a{i}_0{i}_g}{0.377r}+B)\frac{v_a{i}_0{i}_g}{0.377r}$

Separate this equation, can get:

$i_g=0.377\frac{r}{i_0{v}_a}\&CenterDot;\frac{1}{2A_i}(\sqrt{B_i^2+38196A_i\mathrm{Pe}}-B_i)---\left(5\right)$

The velocity ratio of being tried to achieve is compared with the speed changer of sample car, get higher gear near this value as current shift;

x＝min|i _g-i _x| (6)

P wherein _iEngine power during for engine output torque.

2. according to definite method of the said a kind of step change transmission economy retaining velocity ratio of claim 1, it is characterized in that the said constant A of confirming according to the data of engine type _i, B _iFor for any motor, according to formula (1)-(6), obtain the Best Economy performance plot through test method, after it is similar to, can obtain the A in the formula (2) _i, B _iAccording to the engine torque and the tach signal of sensor acquisition, determine the power P of motor then _e, the GES v that combines load and road condition change to gather in addition _a, calculate needed velocity ratio according to formula (5), determine current gear according to formula (6) again, motor is moved along the economical operation line to the full extent.

Images